Hi Lisa,

Have alook at these articles:

https://www.researchgate.net/publication/223980073_Extraction_of_DNA_suitable_for_PCR_applications_from_mature_leaves_of_Mangifera_indica_L

https://www.researchgate.net/publication/230575117_A_high_throughput_DNA_extraction_method_with_high_yield_and_quality

https://www.researchgate.net/publication/49818279_Rapid_and_efficient_isolation_of_high_quality_nucleic_acids_from_plant_tissues_rich_in_polyphenols_and_polysaccharides

https://www.researchgate.net/publication/262023657_Rapid_and_Efficient_Isolation_of_High-Quality_Small_RNAs_from_Recalcitrant_Plant_Species_Rich_in_Polyphenols_and_Polysaccharides.

Hope it will help. All the best.

Article Extraction of DNA suitable for PCR applications from mature ...

Article A high throughput DNA extraction method with high yield and quality

Article Rapid and Efficient Isolation of High Quality Nucleic Acids ...

Article Rapid and Efficient Isolation of High-Quality Small RNAs fro...

Polysaccharides  co-precipitating with nucleic acids are main problem for DNA/RNA isolation from plants. I know several tricks though success is not guaranteed: 1) dissolve pellet in 100 ul of the DEPC-treated 0.5% SDS and, store at -80C for a while or overnight, spin at high speed and re-precipitate RNA with NaAc-alcohol; 2) dissolve pellet in 1M NaCl-10mM tris-HCl- 2mM EDTA (pH=8.0) add 0.3x volume of 100% ethanol, mix well, spin down at high speed for ~10 min. Carefully transfer supernatant to new tube (keep in  mind, pellet may be clear and almost invisible) and add  1.7x volume (or 2.7x if you wish for RNA) 100% ethanol, 1ul glycogen (for RNA) and 1/10 volume of 3M NaAc; 3) try to treat with cell-wall degrading enzymes followed by chloroform/iso-amyl alcohol treatment.  Please keep in mind that traces of salts might be not compatible with downstream applications. I usually increase number of washes with 70-80% alcohol.  

Hi Lisa,

I am working with potato tubers - very rich in starch and I got really nice RNA using protocol I have published in this paper:

https://www.researchgate.net/publication/261798279_The_Adaptation_of_Silica_Capture_RT-PCR_for_the_Detection_of_Potato_Virus_Y

I do not know procedure with dialysis for RNA isolation, could you share the protocol involving it ?

Article The Adaptation of Silica Capture RT-PCR for the Detection of...

You can use plant RNA exptraction kit.

https://www.qiagen.com/hk/products/catalog/sample-technologies/rna-sample-technologies/total-rna/rneasy-plant-mini-kit

Dear Dong, The thing is that commercial kits, very nice and very good for most applications, not always performs well for samples rich in polysaccharides and/or polyphenols. 

I briefly looked through protocol that Krzysztof mentioned.  As far as I understand, same chemistry is used in Qiagen kit.  Indeed It should work well. However, if we are talking about time saving strategy, scaling up the Qiagen kit-based DNA extraction will be faster.  Also, when you filter a DNA-containing solution through the silica gel layer on the top of membrane (in the Qiagen column)  you will get more efficient binding of DNA compared with that from low-concentrated DNA solution.  

 Thank you all for your advice.  I have tried Qiagen's RNeasy Plant Mini kit with and without several modifications.  Opuntia consistently clogs the silica filter.  CTAB and SDS based extraction buffers do just as poorly.

The only way I've gotten anything is using Trizol with potassium acetate clean ups.  However, even with the KOAc (single and multiple treatments) there is still significant polysaccharide contamination that interferes with the magnetic bead chemistry for rRNA depletion and RNA clean ups. 

Before giving up, try silica in suspension, as I mentioned before. It may require optimization of your homogenisation buffer but for potato tuber it works just on extracted sap.